Obsidian vs Tourmaline – The Similarities and Differences (With Photos)

By Keith Jackson - Geologist

| Updated

Obsidian vs Tourmaline – The Similarities and Differences (With Photos)

By Keith Jackson - Geologist


Obsidian and tourmaline might sit side by side in a collector’s cabinet, but they’re totally unique from each other. One looks like a piece of the night sky, while the other is like a rainbow trapped in a crystal.

If you’re curious to know the differences between obsidian and tourmaline, you’re in for a treat!

In this article, we’ll explore the properties that make them distinct as well as the characteristics that they share. Here, you’ll understand why these rocks have such diverse uses for us: as tools, as beautiful jewelry, and even for healing.

As we compare obsidian vs tourmaline, you’ll be surprised at how they can help us understand the world around us. Let’s start unraveling the mysteries of these two natural wonders!

Obsidian vs Tourmaline – The Major Differences

Obsidian and tourmaline may be both fascinating, but they are as different from each other as can be. In fact, their distinctness goes beyond their looks. Below are their major differences:

Color – Obsidian is commonly black or dark-shaded

A glossy, black raw obsidian specimen
Obsidian photo provided by and available for purchase at EthixCrystalCo

When you look at obsidian, you might think you’re peering into the depths of space. It’s usually a deep, dark black color, like the midnight sky.

Sometimes, it can have streaks of brown or spots of green and even a silvery sheen. This is because tiny bubbles or minerals got trapped inside it as it cooled down super quickly from lava.

Tourmaline, on the other hand, is the opposite— it parties in color! It can be found in almost every color you can think of.

There’s black tourmaline, which is pretty common, but there are also ones that are pink, green, blue, and even watermelon-colored with green on the outside and pink in the middle. Some can even change color depending on the light.

What’s wild is that the same kind of tourmaline can look different based on where it comes from. Like, a green tourmaline from Brazil might be a different shade than a green tourmaline from Africa.

Luster – Tourmaline’s luster can vary from vitreous to resinous

A raw green tourmaline showing textured surface
Green tourmaline photo provided by and available for purchase at GemstoneJewelryA

Obsidian is like a piece of shiny black glass. When you hold it up to the light, it looks glossy, kind of like when you see the sun reflect off a calm lake.

That’s because it’s volcanic glass, and just like the glass we use in windows and bottles, it has a smooth, shiny surface that reflects light directly back, making it look bright and clear.

Tourmaline, with its many different colors, has a luster that can be a bit more like a disco ball, with lights bouncing in different directions. It’s usually shiny too, but not in the same glassy way as obsidian.

When light hits tourmaline, it can reflect off in many directions because of how it’s shaped and sometimes because it’s not perfectly smooth. Its surface can be a little uneven, and it might not reflect light as clearly as obsidian does.

So, we could say that obsidian is like a flashlight, with a strong, direct beam of light, while tourmaline is more like a lantern, with a softer, more scattered glow.

Crystal Structure – Obsidian does not have a crystal structure

Pieces of raw and rough obsidians
Obsidians photo provided by and available for purchase at EarthsMineralsInc

Obsidian doesn’t have an orderly structure. It cooled down so fast from molten lava that its tiny pieces didn’t get a chance to line up in a neat pattern. That’s why, instead of forming crystals, obsidian is smooth and looks like glass.

On the other hand, tourmaline’s crystals are all arranged in a special, repeating pattern, kind of like a honeycomb or a spiral staircase.

In fact, this rock often forms long, skinny crystals that can look like pencils or hexagons when you slice them crosswise.

The difference in how obsidian and tourmaline are put together is pretty neat because it tells us a story about how they were formed.

Obsidian’s hasty freeze means it’s more random and smooth, while tourmaline’s careful crystal structure shows it took its time, growing slowly, allowing it to make those distinctive, orderly patterns.

Cleavage – Tourmaline exhibits poor to indistinct cleavage

Five pieces of raw schorls or black tourmaline
Schorls photo provided by and available for purchase at SpiritualStonesStore

Cleavage in rocks is how they break. If we think of breaking a chocolate bar along its squares, that’s kind of like a rock’s cleavage, the natural lines where it likes to break.

Obsidian is like that chocolate bar if it had no squares at all. When you try to break it, it’ll just shatter into sharp pieces with curvy edges. That’s because it doesn’t have cleavage.

It breaks in a random, glass-like pattern, which is why it has smooth and curvy breaks called conchoidal fractures. It’s like dropping a thick glass bowl on the floor— it breaks into curved shards.

Tourmaline, though, does have a favorite way to break, but it’s not perfect. Imagine our chocolate bar has super faint lines; you can still break it along those lines, but it won’t be as neat.

That’s tourmaline’s cleavage for you. It’s not as clear or as smooth as some other minerals, but it’s there. When it breaks, it tends to split along these weak planes but in a kind of choppy way, not clean and straight.

Density – Obsidian feels lighter and has lower density

Massive piece of raw black obsidian
Obsidian photo provided by Jess | Crystal Shop

Density is all about how much stuff is packed into a rock. Like a suitcase, the more stuff it has, or the heavier the stuff inside it is, the denser the rock is.

Obsidian is kind of like the suitcase that’s not too full. It’s got space because it’s made of volcanic glass with lots of tiny holes where gas used to be. That makes it less dense.

So, even though obsidian can look heavy because it’s so dark and glassy, it’s not as packed with stuff as some other rocks.

Tourmaline, on the other hand, is like a suitcase that’s packed. It’s got a lot of different elements like iron, magnesium, and sometimes even gold, all squeezed in there. This means it’s denser than obsidian.

When you pick up a piece of tourmaline, it might surprise you by how heavy it feels, especially if it’s not that big. It’s like when you pick up a small bag and find out it’s packed with books.

Hardness – Tourmaline is harder and more resistant to scratching

A beautiful pink tourmaline with violet crystals attached
Pink tourmaline photo provided by Weinrich Minerals

In the rock world, there’s a special scale used to measure their hardness called the Mohs scale. It scores rocks from 1 to 10, with 10 being the toughest.

On the Mohs scale, obsidian scores about a 5 or 6, which means it’s as tough as glass. You could scratch it with a piece of quartz or even a steel file. It’s pretty solid, but it’s not the toughest kid on the block.

If you tried to scratch your window with obsidian, you might leave a mark, but it wouldn’t shatter.

Tourmaline is the tougher one. It scores higher on the Mohs scale, around 7 to 7.5. That means it can scratch glass and even metals that are softer than it.

This makes tourmaline a bit trickier to shape into things like jewelry because it’s so tough. But that toughness also means it’s more likely to last a long time without getting all scratched up.

Composition – Obsidian is mostly made of silica

A raw black obsidian with a golden sheen
Obsidian photo provided by megzgemz

Different ingredients can make cookies taste different, just like different stuff inside rocks can make them look and act differently.

Obsidian’s recipe is pretty simple. It’s mostly made of silica, the same stuff you find in sand. Imagine if a cookie was mostly flour, that’s how obsidian is with silica.

It’s also got a bit of water and some other minerals mixed in, which can give it those cool colors and patterns. But because its ingredients mix super fast when it’s cooling down from lava, they don’t have time to form crystals.

Tourmaline’s recipe, in comparison, is way more complicated. It’s like a cookie with lots of different chips and nuts. It can have all kinds of stuff in it: aluminum, iron, magnesium, sodium, lithium, or potassium.

All these ingredients can change how tourmaline looks and acts. Some of them can make it magnetic, and the different mixes can give it all those amazing colors we see, from pinks and greens to blues and even blacks.

Formation – Tourmaline is formed from hydrothermal activity

An ocean blue tourmaline with dark blue terminations
Ocean blue tourmaline photo provided by @finemineralphotography and Gerhard Wagner Collection

If obsidian and tourmaline were food, they’re like dishes made in totally different kitchens.

Obsidian is made in a hurry-up kind of way. The Earth heats up rocks until they’re melted, like lava.

Then, in places where volcanoes erupt, this lava cools off super fast, not giving any time for crystals to grow. That’s why obsidian ends up looking shiny and smooth, almost like black glass.

Tourmaline, on the flip side, takes its sweet time to form. It usually grows in places where there’s a lot of heat and pressure over a long time, like deep inside the Earth’s crust.

Sometimes hot water underground helps to add different minerals that make tourmaline colorful. These conditions let its crystals grow big and strong, and that’s why it has those neat, long shapes.

Magnetism – Obsidian is not magnetic

A beautiful, colorful rainbow obsidian with glossy shine
Rainbow obsidian photo provided by Weinrich Minerals

Obsidian and tourmaline react to magnets differently because of what’s inside them.

You could wave a magnet over obsidian all day, and it just wouldn’t stick. That’s because it’s mostly made of stuff that isn’t magnetic.

It’s like volcanic glass, and glass isn’t attracted to magnets. So, if you’re looking for a rock that’s going to stick to a fridge magnet, obsidian isn’t it.

Now, tourmaline is more interesting when it comes to magnets. Some kinds of this rock, especially the ones that are rich in iron, feel the pull of a magnet. It’s not like they’ll leap out of your hand towards a magnet, but they might feel a little tug.

That’s because the iron inside it acts like a tiny magnet itself. Not all tourmaline is magnetic, though; it depends on what kind it is and how much iron it’s got in it.

Fluorescence – Tourmaline may fluoresce

A beautiful elbaite tourmaline with a mix of pink and green hues
Elbaite tourmaline photo provided by Collector’s Edge Minerals – @collectorsedgeminerals

Not all rocks can fluoresce, but some have this awesome ability to light up under a special kind of light called ultraviolet light.

Obsidian doesn’t have this property. If you shine a UV light on it, it’s going to just sit there looking the same as it always does.

It doesn’t glow because it doesn’t have the right minerals to get excited by the UV light.

Meanwhile, some types of tourmaline can glow under UV light. When they do, they can glow in cool colors like red, green, or blue. It depends on what kind of tourmaline it is and what kind of stuff is inside it.

If you’re out rock hunting with a UV light, don’t expect obsidian to put on a light show. But with tourmaline, you might just find a piece that lights up like a little gemstone star in the night sky.

Conductivity – Obsidian is a poor conductor of electricity

A raw black obsidian with glossy shine
Obsidian photo provided by Surry Hills Stones

Conductivity is all about how well something can pass electricity through it. Rocks can be conductive too, but obsidian and tourmaline play this game differently.

Obsidian doesn’t conduct electricity well at all. If you tried to pass an electric current through a piece of this rock, it wouldn’t go anywhere.

It’s because obsidian is like glass, and glass is great for insulating, which means it stops electricity from moving.

On the other hand, tourmaline has a trick up its sleeve. While it’s not going to conduct electricity like a copper wire, it has something called piezoelectricity. This means it can create an electric charge when it’s squeezed or heated.

It means that, under the right conditions, tourmaline can give off electricity. It’s not quite like conducting electricity from one place to another, but it’s tourmaline’s own kind of electricity magic.

Location – Tourmaline can be found in more places

A breathtakingly green chrome tourmaline specimen
Green tourmaline photo provided by Saphira Minerals

Rocks pop up in different spots depending on how they’re made. Obsidian and tourmaline are like two types of people from totally different hometowns.

Obsidian is usually hanging out near volcanoes. That’s because it’s born when lava from a volcano cools super fast.

So, if you want to find obsidian near you, check out places that have had volcanoes in the past. For more information, you ca also read our article on the best rockhounding locations here.

In comparison, tourmaline loves to grow in places where there’s been a lot of pressure and heat over a long time. This means it can be found in a bunch of different settings. It could be in a desert or high up in a mountain range.

Some of the best places to find tourmaline are far-off places like Madagascar, Brazil, and even parts of California in the U.S. To know more crystal hunting sites where you can find them, check out our article.

Price – Obsidian is more affordable

A large black obsidian with amazing shine
Obsidian photo provided by Kibō

Because it’s pretty common and can be found in large chunks, obsidian’s price is not too high.

You might find cool pieces that cost a bit more because they’re super shiny or have unique colors or shapes. But even then, it’s usually affordable enough to add to your rock collection without breaking the bank.

Tourmaline, on the other hand, is rarer and often comes in all these amazing colors that can make it valuable. The value of tourmaline, especially the ones that are clear and bright, can get pretty high.

And if the rock is big and doesn’t have any cracks or chips, the price can go way up. It’s like comparing a regular bike to a high-end racing bike: they both get you places, but one has a lot of extra value because of what it’s made of and how it looks.

Obsidian vs Tourmaline – The Similarities

Not all beautiful rocks have many similarities, and this cannot be more true when you compare tourmaline vs obsidian. In fact, we only found one major characteristics shared by these two:

Streak – Tourmaline and obsidian both have white streaks

A fascinating liddicoatite tourmaline with visible inclusions
Liddicoatite tourmaline photo provided by Mineral Masterpiece

When geologists want to figure out what kind of rock they’ve got, they often do a simple test called a streak test. Rocks can be tricky, though. They might look one color on the outside but leave a different color line, or streak, on a special plate.

But here’s where obsidian and tourmaline are like twins. No matter what color they are on the outside, when you do a streak test, they both usually leave a white streak.

It’s surprising, especially with obsidian, which is so dark and shadowy. You might think it would leave a black line, but it goes against the odds and gives a white streak.

Tourmaline, with all its wild colors, also leaves a white streak. It doesn’t matter if it’s pink, green, blue, or black, its streak is always white.

This reminds us that looks can be deceiving, and sometimes, to know what you’ve got, you have to look beyond the surface.

The Easiest Ways To Tell Obsidian and Tourmaline Apart

A large specimen of black obsidian
Obsidian photo provided by CRYSTALS & LOVE

If you’re holding a specimen that’s probably either an obsidian or tourmaline, but you just can’t tell for sure, you might want to try the following simple tests:

Examine its color

When trying to tell obsidian and tourmaline apart, color is one of the first things you should check out.

Obsidian’ color is like the night sky or a shadow. It’s usually a solid, dark color, and while it might have some streaks or spots of other colors like green or brown, it’s mostly going to stick to that dark theme.

But if you’ve got bright pinks to deep greens, electric blues, and even some earthy browns, that’s more like tourmaline. It’s famous for showing up in a whole bunch of different colors. Sometimes, it even has more than one color in a single crystal.

Feel its texture

When you run your fingers over obsidian, it’s smooth sailing, like sliding your hand over a piece of polished glass. Because it cooled so quickly from lava, it didn’t have time to form any bumps or rough spots. It’s glassy and usually very sleek.

Tourmaline, with its more complex birth story, has a certain texture to it. If obsidian is a smooth lake, then tourmaline is more like a mountain path, with all its ups and downs.

It’s often got ridges or striations that you can feel, much like the grooves on a vinyl record or the ridges on a key.

Look at its shine

When you hold a piece of obsidian up, it’s like turning on a flashlight in a dark room– the shine is bright and direct, almost mirror-like. This is thanks to its glassy nature. Its shine is so glossy that you can use it to check your hair or teeth before a photo.

Tourmaline’s shine, meanwhile, is more like candlelight. It’s shiny, but the light dances around a bit more. This is because of its textured surface.

Its shine can sometimes be so strong it’s almost glassy, especially on a well-cut gemstone. But more often, it’s got a depth to it, like light bouncing off a lake with gentle waves.

About Keith Jackson - Geologist

Keith Jackson is an avid rockhound who is constantly exploring new sites to expand his collection. He is an active Geologist with a wealth of experience and information from across the country that he loves to share with the Rock Chasing crew.

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